Funding for a multinational force to combat Boko Haram's deadly Islamist insurgency in West and Central Africa remains well short of its target, an African Union official said on Tuesday.

So far donors, including Nigeria and France, have pledged about $250 million to fund the 8,700-strong regional force, the African Union's Peace and Security Council said after a meeting in Addis Ababa to discuss funding.

The talks followed the militia's latest attack, which killed at least 65 people in northeast Nigeria on Saturday.

The $250 million includes both previous pledges and those made during Monday's conference, said Orlando Bama, communications officer for the African Union's Peace and Security Council. He did not give further details.

That covers just over a third of the $700 million budget announced for the Multi-National Joint Task Force (MNJTF) last year.

The task force - to be made up of regional African militaries - has yet to mobilize. Instead, national armies are tackling Boko Haram individually, but they often cannot follow the insurgency across the region's long, porous borders.

The region threatened by Boko Haram is one of the poorest in the world, and all the countries in the task force, barring Benin, are oil producers whose budgets have been battered by falling prices.

Boko Haram has killed thousands of people and driven more than 2 million people from their homes during its six-year insurgency.

Regional armies from Niger, Chad, Nigeria and Cameroon mounted an offensive against the insurgents last year that ousted them from many positions in northern Nigeria. The United States has also sent troops to supply intelligence and other assistance.

But progress has been slow.

"The answer lies in there being political will and the capability to back the force," said Imad Mesdoua, at Africa Matters consultancy in London. "This has been a regular problem with multi-national task forces in Africa."